1. Field of the Invention
This invention relates generally to an electrical architecture for a vehicle that includes an electric power take out (EPTO) circuit for providing AC power from the vehicle power sources to an external load and, more particularly, to an electrical architecture for a vehicle that includes an EPTO circuit for providing AC power from the vehicle power sources to an external load, where the EPTO circuit employs a bi-directional DC/DC power converter and a power inverter module (PIM) that are existing electrical devices on the vehicle for other purposes.
2. Discussion of the Related Art
Electric vehicles are becoming more and more prevalent. These vehicles include hybrid vehicles, such as the extended range electric vehicles (EREV), that combine a battery and a main power source, such as an internal combustion engine, fuel cell systems, etc., and electric only vehicles, such as the battery electric vehicles (BEV). All of these types of electric vehicles employ a high voltage battery that includes a number of battery cells. These batteries can be different battery types, such as lithium ion, nickel metal hydride, lead acid, etc.
Most fuel cell vehicles are hybrid vehicles of the type referred to above that employ a rechargeable supplemental high voltage power source in addition to the fuel cell stack, such as a DC battery or an ultracapacitor. The power source provides supplemental power for the various vehicle auxiliary loads, for system start-up and during high power demands when the fuel cell stack is unable to provide the desired power. More particularly, the fuel cell stack provides power to a traction motor and other vehicle systems through a DC voltage bus line for vehicle operation. The battery provides the supplemental power to the voltage bus line during those times when additional power is needed beyond what the stack can provide, such as during heavy acceleration. For example, the fuel cell stack may provide 70 kW of power. However, vehicle acceleration may require 100 kW or more of power. The fuel cell stack is used to recharge the battery at those times when the fuel cell stack is able to meet the system power demand. The generator power available from the traction motor can provide regenerative braking that can also be used to recharge the battery through the DC bus line.
U.S. patent application Ser. No. 12/791,632 titled, Vehicular Electrical Systems, filed Jun. 1, 2010, assigned to the assignee of the present application and herein incorporated by reference, discloses an electrical system for a fuel cell vehicle that includes circuit components for providing AC electrical power to electrical loads external to the vehicle. The electrical system includes a bi-directional DC/DC power converter electrically coupled to the high power voltage bus on which high voltage is provided to the vehicle systems from a fuel cell stack and a high voltage battery, including the vehicle's electric traction system. The bi-directional DC/DC power converter provides a regulated DC voltage that remains substantially constant as the voltage on the high voltage bus fluctuates. The stable DC power from the bi-directional DC/DC power converter is provided to a separate power inverter module (PIM) that converts the DC power signal to an AC power signal. An AC receptacle is coupled to the PIM so that the external loads can be plugged into the receptacle to draw the AC power.
The vehicle electrical system described in the '632 application requires a supplemental bi-directional DC/DC power converter in addition to the existing bi-directional DC/DC power converter provided on the high voltage bus between the battery and the fuel cell stack. Also, the electrical system described in the '632 application requires a supplemental power inverter module to convert the DC power signal from the supplemental DC/DC power converter to an AC power signal in addition to the already existing PIM that converts the high voltage DC power signal to an AC signal suitable for the vehicle's electrical traction system. These components add cost, weight and complexity to the vehicle.